The present invention relates to a continuously variable transmission for a motor vehicle including an engine which the transmission is drivingly connected to, and more particularly to a control apparatus and a control method for such continuously variable transmission.
The conventional continuously variable transmission is shiftable in reduction ratio in accordance with one of a plurality of patterns or schedules. Upon making a change from one to another schedule among the plurality of schedules, a target value of a predetermined control variable such as a target engine revolution speed is subject to a step-like change. This causes the transmission to shift quickly in such a direction as to bring an actual value of the predetermined control variable into agreement with the target value. Thus, the engine revolution speed is subject to a rapid change.
When a change is made from one schedule to another in order to produce more power for acceleration, the continuously variable transmission shifts down rapidly to force the engine to increase its speed rapidly. The inertia torque induced by this rapid engine speed increase absorbs torque produced by the engine, resulting in a temporary reduction in driving power for accelerating the vehicle, thus degrading ride feel for acceleration.
An object of the present invention is to control a continuously variable transmission such that the above-mentioned power interruption is eliminated to give an improved ride feel for acceleration.